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<head>
<meta charset="UTF-8">
 <meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>Document</title>
<script src="../vue.js"></script>
</head>

<body>
    <!-- 
        在vue渲染的过程中 diff算法是一直在工作的,但是diff算法的比较是默认按照顺序依次比较的
        如果说我们逆序添加数据,则很可能diff算法的对比错位了
        所以我们在列表渲染的时候要添加一个唯一的key,diff算法的比较就变成了key对应的新旧虚拟Dom的比较

     -->
<div id="app">
    <button @click="addPersonBefore">在前边添加一个人</button>
    <button @click="addpersonAfter">在后边添加一个人</button>
    <ul>
        <li v-for="item in persons" :key="item.id">
            姓名: {{item.name}} ---年龄 {{item.age}}
        </li>
    </ul>
    </div>
    <script>
        Vue.config.productionTip=false;
        const vm =new Vue({
            el:"#app",
            data() {
                return {
                    persons:[
                        {id:'001',name:"laowang",age:19},
                         {id:"002",name:"xiaowang",age:20},
                         {id:"003",name:"zhongwang",age:9},
                       
                    ],
                };
            },
            methods:{
                addPersonBefore(){
                    this.persons=[
                        {id:Date.now(),name:"dawang",age:22},
                        ...this.persons,
                    ];
                },
                addpersonAfter(){
                    this.person=[
                        ...this.persons,
                        {id:Date.now(),name:"wangzhongwang",age:32},
                    ];
                },
            },
        });
   

 
 </script>
</body>

</html>